Control for vaporizing oil burners with electric ignition



June 2, 1953 JUDSQN 2,640,648

CONTROL FOR VAPORIZING OIL BURNERS WITH ELECTRIC IGNITION Filed Oct. 16, 1950 3 h ts- 1 //\/A//\/7'UR ALBERT L. JUDSON June 2, 1953 A. JUDSON 2,640,648

CONTROL FOR VAPORIZING OIL BURNERS WITH ELECTRIC IGNITION Filed Oct. 16, 1950 s Sheets-Sheet 2 L1 L2 E.- Z. 117 [/5 z4 1m uw/e 7'0 R ALBERT L. JUDDON flTTUR/VES June 2, 1953 JUDSQN 2,640,648

CONTROL FOR VAPORIZING OIL BURNERS' WITH ELECTRIC IGNITION Filed Oct. 16, 1950 3 eetset 5 L1 If E5.

mu/v TUR ALBERT L. JUDSON ,4 7' TE A/11% Patented June 2, 1953 CONTROL FOR VAPORIZING OIL BURN ERS WITH ELECTRIC IGNITION Albert L. Judson, Portland, Oreg., assignor to Iron Fireman Manufacturing Company, Portland,

Oreg.

Application October 16, 1950, Serial No. 190,316 Claims. (01. 236-1) My present invention comprises the addition of an automatic electric control circuit and mechanism to the Combination Oil Burner Inlet and Igniter of my patent application S. N. 174265 filed July 17, 1950. My application S. N. 174,265 discloses a combination oil inlet and igniter applied to a vaporizing oil burner of the type comprising a combustion receptacle in which oil is progressively evaporated for continuous combustion by the heat of combustion and to which combustion air is progressively supplied to complete the combustion of the oil. In substance the oil inlet and igniter combination of that application comprises a separate, small, intermittently operated; electrically ignited oil burner which produces an ignition flame outside the main burner simultaneously with the introduction of oil into the main burner and injects into the main burner at starting an ignition flame. My present invention comprises, in combination therewith, means for safely controlling the operation of the ignition oil burner together with the control of the supply of oil and air to the main burner, all in response to the requirements for heat as relayed to the control by a condition responsive instrument such as a space thermostat.

It is the principal object of my invention to provide a vaporizing oil burner system which can be automatically operated and controlled by a condition responsive instrument and which will neither be required to be manually ignited nor required to maintain a pilot flame when there is no call for heat.

It is a second object of my invention .to supply my system with a safety means adapted to test the main burner for the successful completion of the ignition function and to shut off the igniter when ignition is complete.

It is a third object of my invention to start instantaneously a limited flow of oil to the main burner and the ignition burner on a call for heat and then to gradually increase the rate of oil flow to the main burner as ignition is established.

It is a fourth object of my invention to prevent the attempted ignition of the burner while the temperature of the main burner combustion receptacle is above a predetermined temperature.

It is a fifth object of my invention to assure a supply of combustion air to the main and ignition burners whenever a cycle of operation is started in response to the condition responsive control.

It is a sixth object of my invention to maintain burner.

tion with the combustion receptacle of the main burner after the call for heat has been satisfied and until the combustion receptacle temperature has been reduced to a pre-determined safe starting value.

It is a seventh object of my invention to stop the supply of oil instantaneously to the burner when the call for heat has been satisfied.

It is an eighth object of my invention to provide means for modulating over an effective range of supply of oil to the burner in response to the heat requirements of the heating load.

It is a ninth object ofmy invention to provide a simplified operating system where all of the above objects are not necessary of attainment.

It is a tenth object of my invention to provide means for programming the supply of combustion air to the ignition burner in accordance with the operating characteristics of the burner.

How these and other objects are attained will be apparent on reference to the following description referring to the attached drawings in which:

Fig. 1 is a schematic drawing of the mechanism and circuit of my more complete invention.

Fig. 2 is a simplified schematic drawing of the circuit. of Fig. 1.

Figs. 3 and 4 are variations of the condition responsive circuit of Figs. 1 and 2.

Fig. 5 is a schematic representation of a simplified form of my invention.

In the figures like reference characters refer to like parts.

Referring now to the drawings there is shown an electric motor II driving a fan I2 adapted to deliver atmospheric air for combustion from the outside to the inside of a plenum chamber formed between a main oil burner oil vaporizing or combustion receptacle I3 and an outer enclosure I4 having an air entrance hole I5 in its bottom and an inspection hole I6 at one side closed by a cover I! secured to enclosure I4 by screws I8. Receptacle I3 has an upwardly curved bottom member I 9 for reducing the supply of oil it can hold below a given oil level 20 as well as to control the vaporizing oil. Holes H for the injection of combustion air into receptacle I3 are of such size and arrangement as are found best adapted to the duties of the particular design of Cast iron top member 22 rests on the horizontal top flange of receptacle I3 and is for the purpose of forming the reduced diameter flame outlet. 24 for receptacle I3. Shown broken off is the upwardly extending combustion chamber 25 of the heat exchanger to which the burner is attached in use. Arrows show the path of the 3 combustion air into receptacle l3 and the discharge of flame and products of combustion therefrom.

Threaded into half coupling 26 welded to r ceptacle I3 is ignition oil burner body 2'! which together with the upwardly extending walls 28 form a well for the electric igniter comprising a nickel chromium resistance wire 29 and a capillary wick 38. The ends of wire 29 are crimped into terminal fittings 3| and 32 secured into insulating cover 33 sealed by screws 34 to the top of walls 28 of body 21. An air .port ,35'formed in wall 28 is selectively closed by valve disk 3i; having valve stem 38 extending rearwardly. through, port 35 and havin pin 31 through, the endthereof to limit the forward motion of valve disk 35. The forward extending end of stem 38 is shouldered as shown and has its reduced end section headed to confine strut spring 39 and disk loosely thereon. The endsof strut spring 39 are confined in recesses formed in the legs of ushaped leaf spring M, as shown. The base of U spring 4| is riveted to bimetal blade 42 which in turn is secured to the body 21 by screws 43. Electric resistance type heater 44 is insulatedly carried on bimetal 42. The details of the foregoing parts are perhaps more clearly shown in my prior application above noted. The position of valve 36 shown in the drawing is slightly away from port 35 as would be the case when bimetal 42 is at room temperature and the ends of the U spring M rest against wall 28. As heater A l is energized bimetal 42 flexes in a clockwise direction carrying the valve mechanism with it until pin 37 strikes the inside of wall 28 and stops the opening motion of disk 36. As blade 42 continues to flex, strut spring 39is held and forced over'center, giving disk 35 a sudden movement towards port 35 but'diskyi is prevented from closing 13011135 by the action of disk 48, the periphery of which limitsthe possible amount of rearward iiexure of strut spring 39. It is seen therefore that all the time blade 42 is flexing in a clockwise direction,'valve disk 33 is away from port 35 and the port isopen to the passage of air.

But due to pin 31 and'the cocking action of spring 39, disk 36 is never far away from port '35 so that whenever blade 42' starts to cool and flex in a counterclockwise direction, disk 36 will close port 35 almost immediately; As blade 42 continues to cool, the shoulder on stem 38 presses on spring 39 and forces it 'overcenter inthe forward direction thus again opening port 35 to the passage of air. Further cooling of blade 42' causes the legs of U spring M to again come to rest against wall 28 as shown. It is seen that throughout this heating and cooling cycle of blade 42, port 35 is always open except for an interval after blade 42 starts tocool.

Secured by screws 45 to supporting legs 46 welded to receptacle I3 is insulating body 41 of temperature responsive single pole, double throw, snap acting, switch 48, whose dished bimetal actuator 49 is loosely confined at its periphery between the extendedrflanges of legs 46 and guide member 58 secured by screws 45. Secured to insulatin body 4-7 by terminal screws El, 52, and 53, respectively, are switch blade 5 3, cold contact 55, and hot contact 55, blade 54being resilient and biased to contact with cold contact 55, and to cause insulating operating stem 51 loosely guided in member to follow but not crowd bimetal disk 49. When the receptacle l3 attains a predetermined temperature, disk 49 goesforwardly over center witha snap action and, through stem screw 85; Coil 89 57, causes blade 54 to leave contact 55 and suddenly contact contact 55. On cooling, the reverse action takes place.

A continuous supply of burner oil is available by gravity feed to constant level oil container 58 through supply pipe 59 and port 6! controlled as shown schematically byneedle valve 60 actuated by-fioat 62 to maintain the oil level 25 in container 58. Needle valve 63 on stem 84 cooperates with port 65 to control the supply of oil from container 58 through pipe 56 to the main burner receptacle l3 through ignition burner bod-y 2'1; Stem 64 is biased upwardly by coil spring 67 confined between disk 68 secured to stem iiiand'cover 63' secured by screws H! to container 53. Secured to cover 68 by screws H is bimetal blade E2, the bifurcated end of which straddles stem at in position to restrain the upward movement of stem 64 under the bias of spring Bl. It should be noted that with valve 63 closing port 55 as shown with blade 12 at room temperature, there is some pro-determined clearance between the bifurcated end of blade 12 and the upper side ofdisk 58 so that stem 54 could" move upwardly and allow oil to flow into receptacle 3 at a low rate when the upward movement of stem 54 is limited by blade '12 in itscold condition.

Resistance heaters '13 and M having acommon terminal 175 and other terminals respectively "It and ll are insulatedly carried on blade-l2.

Stem M is shouldered at its upper end and its reduced end '58 passes loosely through a hole 19 in bar smaller than themain diameter of stem 64: Bar 8'23 is secured to armature 8 I- carried on hinge leaf '82 hinged as shown to hinge bracket 83, which also secures-the electromagnetic core spring 8'! and allows stem 64 to move upwardlyunder the urge of spring 61' and restraint of blade '52 to a limit position preset by adjusting has terminals ill and 92. Switch operating member '53 of insulating material is guidedin a frame member at 94 andis linked with bar 85 to be moved upwardly and downwardly thereby and take with it resilient switch blades 95, 96 and ill. In the downward position of member-93, blades 95, 86, and 91 are respectively separated from. stationary contact blades 98 99, and Hit, while in the upward position of member 93, blades 95, 9S, and 97 are respectively in contact with blades 98, 99, and H10. Also in the downward position of blade 9? it is in contact with blade lfll. Blades Bl, Hill, and I DI form what is known as an overlapping switch since blade 97 in its mid-position contacts both blades lfiil-and-llll.

At 182 is shown a condition responsive control such as a space thermostat having a stationary terminal I53, a blade (5 1*, a first stationary contact Hi5 and a=secondstationary contact 106.

A control transformer is shown to have primary terminals ml and (08 andsecondary terminals I09 and 5 M. An ignition transformer is shown to have primary terminals HI and H2 and secondary terminals H3 and H4. 'A limit control is shown 'to have terminals H5 and H6,

although the use of such an instrument is optional. The electric supply line terminals are shown as LI and L2.

As shown, electric wire II1 connects terminals LI and H5. Wire H8 connects blades I and 95 with terminals H6 and '5I. Wire H9 connects terminal 52 to blade 98 and terminal I2I of the fan motor. Wire I20 connects terminal 53 with blades 96, and IOI. Wire I 22 connects blade 99 with terminal H2 of the ignition transformer. Wire I23 connects blade 91 with terminal I08 of the control transformer. Wire I24 connects line terminal L2 to control transformer terminal I 01, to ignition transformer terminal I II and to fan motor terminal I25. Low voltage wires I26 and I21, respectively, connect ignition transformer secondary terminals II 3 and H4 to. igniter resistor terminals 32 and 3I and to the terminals of heater 44. Low voltage wire I28 connects control transformer secondary terminal I09 to thermostat blade terminal I03. Low voltage wire I29 connects control transformer secondary terminal IIO to relay coil terminal 9I and heater terminal 15. Wire I30 connects thermostat stationary contact I to heater terminal 11 and relay coil contact 92. Wire I3I connects thermostat stationary contact I06 to heater terminal 16.

The operation of the form of my invention shown schematically in Fig. 1 and in simplified circuit arrangement in Fig. 2, is as follows-In the drawings the parts are shown at room temperature when there is no call for heat. Now

assume that the temperature of the room lowers and thermostat blade I04 moves to the left. and contacts stationary contact I05. Control transformer primary is already energized from LI and L2 through wire II1, the limit control, wire II8, blade 54 and contact 53 of snap switch 48, wire I20, overlapping switch blades I 0| and 91, wire I23 and wire I24. The relay coil 89 is then energized from the control transformer secondary through wire I29, thermostat contact I05, blade I04, and wire I28. The relay armature 82 closes on core 84, rotates bar 80 clockwise and throws switch operating member 93 upward closing switch blade 95 on blade 98, blade 96 on blade 99 and transferring contact of switch blade 91 from blade IM to blade I00. At the same time the downward bias of spring 81 on valve stem 64 is overcome by the relay and spring 61 raises valve 63 from port 65 until further movement is restrained by blade 12 which then gradually begins to rise due to the increasing influence of heater 14 energized when relay coil 89 was energized. The lifting of valve 63 starts oil to flow through pipe 66 into ignition burner body 21 where it contacts wick 30 on its way to burner receptacle I3.

When blade 95 contacts blade 98 the fan motor is energized from LI and L2 through wire I I1, the limit control, wire I I8, switch blades 95, 98 and wires H9 and I24.

When switch blade 96 contacts blade 99 the primary of the ignition transformer is energized from LI. L2 through wire II1, the limit control, wire II 8, blade 54 and contact 55 of switch 48, wire I20, blades 96, 99, and wire I22 and I24. The ignition transformer secondary circuit being always continuous from terminals I I3 and I I 4 through wires I26 and I21 and heater 44 in parallel with igniter wire 29, igniter wire 29 immediately starts to heat up and vaporize and ignite the vapor of part of the oil wicked up by vwick 30, the oil vapor being mixed within the igniter well walls 28 with combustion air urged through air-port 35 by fan I2 as indicated by the arrows in Fig. 1. At the same time heater 44 is influencing blade 42 to'hold air valve 36 open and cock spring 39 for quick closure as previously explained.

As the ignition flame grows it gradually extends out into receptacle I3 over the oil entering receptacle I3 through body 21 and combustion of the oil which has flowed into receptacle I3 is accelerated to the point where the temperature of receptacle I3 has increased sufficiently to influence bimetal disk 49 of switch 48 to snap to the right and transfer contact of blade 54 from contact 55 to contact 56 (or from terminal 53 to terminal 52). When this occurs wire H8 is disconnected from wire I20 and the primary winding of the ignition transformer is no longer energized from LI and L2. Igniter wire 29 cools and heater 44 cools allowing blade 42 to cause air valve 36 to move towards wall 28 and close off the supply of air to the ignition burnerfor a long enough time to snuff out the ignition flame and then to reopen to allow purging air to flow through the ignition burner as long as the fan is in operation. The mechanism of the operator for air valve 36 has been explained above.

Also when switch 48 is actuated by the heat of receptacle I3, blade 54 closes on contact 56 and wire I I8 is connected to wire H9 setting up a holding circuit for the fan motor around switch blades 95, 98 thus assuring the continued operation of the fan until receptacle I3 has cooled sufliciently to allow switch, 48 to snap back to its room temperature position shown. The thermostat is still calling for heat, the main burner has been ignited and is burning oil at the maximum rate allowed by blade 12 as heated by heater 14. Should this amount of heat be insufficient to prevent the room temperature from dropping further, thermostat blade I04 restrained by contact I05 Will bow over against contact I06 thus energizing heater 13 and causing blade 12 to allow valve 63 to open valve port 65 to supply oil to receptacle I3 at a higher maximum rate. As-

suming that burning at this new rate the burner causes the room temperature to rise then thermostat blade I04 will straighten away from contact I06 and the oil flow will be lowered. Should the room heat requirement be between the two maximum oil rates set by heater 14 or by heater 14 plus heater 13, thermostat blade I04 will follow the room temperature and move repeatedly into and out of contact with contact I06 and maintain the average oil flow rate required. Should the oil flow rate set by heater 14 alone be too great to satisfy the heat requirements of the room, then the room temperature will rise sufficient- 1y to move thermostat blade I04 away from contact I05 and both heater '14 and relay coil 99 will be deenergized allowing spring 81 to return all parts except switch 48 to the position shown in Fig. 1. Valve 63 will shut off all oil from the burner but fan I2 will continue to run until all oil has been burned from receptacle I 3 and switch 48- snaps to its cold position. It should be noted that after the thermostat and relay have shut down the burner, neither the primary coil of the switch 48 returns to its cold position, but that y when switch 48 returns to its cold position a new start and cycle of burner operation can be initiated by the; thermostat.

In Figures 3 and-4 are shown alternate methods of modulating the control of the heatsupplied.

byv the oil burner as governed by the rateof: oil

fiow to-the burner aslimited by the position of. bimetal blade I2 as infiuencedby'the heaters shown in Figs. 1 and 2 as 13 and M;

In- Fig. 3 the thermostat is'modified so that-the blade 204 is not itself influenced by heat but-is.

positionedby the bimetallic spiral. which supports blade 204 from fixed terminal I03. Contact 205' is a conducting plate over which blade 204 may slide incontact therewith and contact 206 is a resistor over which blade 284 may slide in contact therewith and thereby change the resistance of the circuit of heater 214. The opera-- tion and cut outresistance from resistor ZIlGthus increasing the current and consequent heat supplied by heater 274 and increasing the oil supply to the burner by the influence of heater 2' on bimetal blade I2 of the oil control mechanism. It is understood. that the thermostat bimetal spiral is sufficiently isolated from heater 206 as not to be largely affected thereby.

In Fig. 4 the thermostat is generally similar to the thermostat of Figs. 1 and 2 but has a thermostat heater 315 added. into the circuit between heater 374 and contact 306. The resistance of heater 315 is small relative to heater 374. In this case when the temperature of the air surrounding the thermostat cools below the set temperature, blade Hi4 contacts with contact 305 and starts the burner on low fire. If this fire is not sufficient to raise the temperature of the room, the blade I04 tries to continue in a clockwise direction butis restrained by contact 305. and bows to the left until it makes contact with 3%, thus energizing heater 314 and increasing the oil supply to the burner as previously explained. As blade I84 continues in contact with 355, the oil supply will be increased to the maxi.

mum capacity of the furnace unless the heat supplied by the furnace becomes sufficient to start the thermostat moving towards its open position. To give better operation and prevent over? shooting of the heat supply, the heater 315 adds a small amount of heat to the thermostat and causes blade I04 to leave contact 306 before it otherwise would. It is thus seen that as long as any heat is required from the furnace, blade I04 will remain in contact with 305 and keep the burner in operation, but by repeatedly contacting with 398 blade I04 causes the oil supply to be modulated to the needs of the heating loads.

Other arrangements for modulating the oil supply to the burner in accordance with the requirements are possible but the examples shown are sufficient to illustrate the methods used. The simplest type of operation, and in many cases the best, would be with a plain on and oil control using a single contact thermostat like the one shown in Figs. 1 and 2 would be with contact I98 eliminated and with wire BI and heater 13' also eliminated from the system. Then the resistance of heater I4 would be such that when up to, temperature the oil supply wouldbe. at the.

maximum rate required fortheload at anytime.

In Fig; 5 is'showna somewhat'simplifi'edfiormi of'my invention to. be used with a natural draft rather than with a forced draft type of burner;

; In other words, Fig. 5 is-substantially Fig; 2 with the combustion air fan motor and its associated circuits and circuit elements eliminated andwith a mechanically operated modulating damper addedto control the combustion air supplied bynatural draft conditions. always desirable or used with natural draft? burnerssince'in many cases in small furnace installations the advantages of securing" complete and sootless combustion is of greatereconomic' value than attaining a greater'theoretical com bustion eificiency as determined by C02 readings and temperature readings of the flue gases;

In Fig. 5 it is seen that from Fig. 2 there has been eliminated hotcontact 52 of switch 48; wires H9; fan motor-IZI, I25, and fan switch 98; Also it is noted that as an optional structure there has been added the damper disk I40 withair'openings MI and rotatingly securedto pin Hi2 fastened to arm I43 biased in a clockwise direction by spring I44 and movable ina counterclockwise direction against the bias of spring I44- by bimetal blade 32 under the influence of heaters '53' and M.

known in'the art. Except for the elimination of the fan motor and its associated circuits and circuit elements the operation of the system shown in Fig. 5 is readily understood from the above explanation of the operation of the system of Figs. 1 and 2.

Having thus completely disclosed two desirable forms of the apparatus of my invention and described four forms of the condition responsive.

circuit thereof and completely explained the operation thereof, I claim 1. A. control system fol-vaporizing oil burner of the type comprising a combustion receptacle in which oil is progressively evaporated for contlDLlOLlS combustion by the heat of said combustion and to which air is progressively supplied open position; a bimetal restraining means in.

initial spaced relation to said second biasing means, means including said second biasing means efiective when said heat responsive means. responds to a call for heat to quickly open said. valve a limited amount determined by said himetal restraining means, and means including an electric heater for said bimetal restraining means energized upon said call for heat to decrease the restraining action of said bimetal' restraining means to allow said valve to be gradually opened to a pro-set full open position by said second biasing means; means cooperating with said condition responsive means to'initiate. the operation of said ignition means; a'cold-closed temperature responsive means associated with saidreceptacle; means adapting said 'tempera- I ture responsive means to terminate the operation of said ignition means; and-means pperatively associated with said temperature responsive means and said condition responsive means torendersaid condition responsive means ineife'c- Such a damper is not" The construction and mounting and related parts of a damper disk such as I40 is well,"

tive to'initiate the operation of said ignition means and to render said first biasing means inefiective when said receptacle is above a predetermined temperature.

2. The system of claim 1 including a fan adapted to supply combustion air to said burner, amotor for driving said fan, means cooperating with said motor and said heat responsive. means to cause-said fan to deliver air to said receptacle whenever said heat responsive means is maintaining said first biasing means ineffective, and means adapted to prevent said heat responsive means for interrupting the operation of saidfan when said receptacle isabove a pre-determined temperature.

3. The system of claim 1 including means'for varying the rate of supply of combustion air supply to said receptacle and means coupling said last named means to said oil valve to increase the air supplied to said receptacle as the oilsupply to said receptacle is increased.

4. The system of claim 1 including additional means adaptedto vary the opening of said valve in response to said condition, said additional meansincludingcircuit means and means in cluded in saidheat responsive means and said electric heater for said bimetal means to increase the current supplied to said electric heater to increase the opening of said oil valve as required by said heat responsive means.

5. A control system for a vaporizing oil burner of the type comprising a combustion receptacle in which oil is progressively evaporated for continuous combustion by the heat of said combustion and to which air is progressively supplied to complet said combustion, said system com-prising: electric ignition means for initiating the ignition of said oil in said receptacle; means adapted to control the flow of oil to said receptacle; a first means biasing said oil flow controlling means to its no flow position; a condition responsive means adapted on a call for heat suddenly to render said biasing means ineffective; a second means biasing said oil flow controlling means to its full flow position; a bimetal means adapted when cold to limit the initial opening of said oil fiow controlling means by; said second biasing means when said first biasing means is ineffective; an electric heater for said bimetal means; means cooperating with said condition responsive means on a call for heat to energize said electric heater and thereby gradually to increase the limit of opening of said oil fiow controlling means by said second biasing means; means cooperating with said condition responsive means on a call for heat to energize said electric ignition means; a cold closed temperature responsive switch means associated with said receptacle; means adapting said temperature res-ponsive means to terminate th operation of said electric ignition means; and means operatively associated with said temperature responsive means and said condition responsive means to render said condition responsive means ineffective to initiate the operation of said electric ignition means and ineffective to render said first biasing means ineffective; whereby on each call for heat by said condition responsive means when said temperature responsive means is in its cold position said electric ignition means will be energized, said first biasing means will be rendered ineffective, said valve suddenly will be opened by said second biasing means to a low limit of oil flow set by said bimetal means, and said oil flow will be increased gradually to a preset high limit; and whereby on each call for heat by said condition responsivemeans when said temperature responsive means is in its hot position the actuation of said electric ignition means and the rendering ineffective of said first biasing means and the heating of said bimetal will be delayed until said temperature responsive'means returns to its coldposition.

6. A control system for a vaporizing oil burner of the type comprising a combustion receptacle in which oil is progressively evaporated ior con-1 tinuous combustion by the heat of said combus tion and to which air is progressively supplied to complete said combustiomsaidsystem comprising: means for controlling the flow of oil to said receptacle; means to ignite said oil in said receptacle; means for suddenly operating said control ling means to stop the flow of oil 'to said receptacle; means for suddenly operating said controlling means to start theflow of oil to said receptacle at a limited rate; means for gradually increasing the limit of said rate of oil flow to said receptacle; a heat responsive means adapted on a call for heat to actuate said oil fiow starting means, said ignition'means and said limit in creasing means; said fiow stopping means being operatively associated with said heat responsive means and adapted to operate when said call for heat issatisfied; and a temperature responsive means adapted to delay the efiectivity of said heat responsive means to start said oil flow and ignite said oil until the temperature of said receptacle is reduced to a safe pre-set value.

7. A control system for a vaporizing oil burner of the type comprising a combustion receptacle in which oil progressively is evaporated for continuous combustion by the heat of said combustion and to which air progressively is supplied to complete said combustion, said system comprising: a source of power; a cold closed space thermostat switch; a cold closed combustion thermostat switch adjacent said receptacle; an oil valve adapted to control the rate of oil fiow to said receptacle; means biasing said valve towards its open position; a bimetal means adapted when cold to limit the opening of said Valve to a pre-set low rate of oil flow therethrough; a circuit including said power source and an electric heater adapted to be energized on the closure of said space thermostat switch and heat said bimetal means gradually to open said valve to a higher rate of oil fiow therethrough; an electric igniter adapted when energized to initiate the ignition of said oil in said pot; a normally open switch; a circuit including said power source and an electrically operated relay adapted to be energized on closure of said space thermostat switch; said relay being adapted, when de-energized, instantaneously to close said oil valve; sa d relay being adapted when energized to close said normally open switch; said igniter, said normally open switch and said combustion thermostat switch being connected in series with said power source, whereby when said normally open switch and said combustion thermostat switch are closed said igniter will be energized and when said combustion thermostat switch is opened under the influence of oil combustion in said receptacle said igniter will be de-energized.

8. The control system of claim 7 including a single pole double throw switch; one throw of said switch being normally open and the other throw of said switch being normally closed and both throws of said switch being closed during the operation of switching from one throw to the actre ses other; said relay being adaptedtoclose said normally openthrow of said double throw switch and to open said normally closed throw of said double throw switch when said relay is energized on closure of said space thermostat switch; said normally closed throw of said double throw switch and said cold closed combustion thermostat switch being in a first series circuit with said power source and being adapted to'permit the energization of said relay and said bimetal heater through said space thermostat switch when all three are closed; said normally open throw of said double throw switch being in parallel with said first series circuit to form a second series circuit with saidpower source to maintain said relay and said bimetal heater energized when said combustion thermostat switch openson a rise-in temperature of said receptacle while said space thermostat switch is closed; and said combustion thermostat switch being adapted to prevent the energization of said relay and said bimetal heater from said, power source when said space thermostat switch closes and said combustion thermostat switch .is open.

9. The control system of claim 7 including. a damper means adapted to control the air supply to said receptacle, and meansloperatively coupling said damper means withsaidoil valve, 'whereby 12 asisaid oil valve is vopened by said'relay and said bimetal means said damper will beupositioned to cause the air supply tovsaid receptacle to increase as the oil supplied to said receptacle is increased.

10. The control system of claim 7, including a fan adapted when driven to supply air tocsaid burner; a motor fordriving said fan; a "hot closed temperature responsive :switch adjacent said receptacle; a second normally open switch connected in parallel with said hot closedswitch and adapted to be closed by said relay whensaid relay is energized; and circuit means adapted to energize said motorirom said-power source through said normally open switch when :said relay is energized and to'maintain 'saidzmotor energized when said hot closed switch is closed and said relay is de-energized.

ALBERT L. JUDSON.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,337,476 Landon-et al. Dec. 21,1943 2,364,591 Stoughtonet al. Dec. 5, 1944 2,416,766 Miller-ct al. Mar; 4, 1947 2,500,663 Cleveland Mar. 14,1950 

